ICAP for SMTP

vey-proxy can use an ICAP REQMOD service for outgoing SMTP DATA messages.

The SMTP message is converted into an HTTP/1.1 PUT request and sent to the ICAP server. The ICAP server’s response is then converted back into an SMTP message in the same format.

See also ICAP Request Headers for the ICAP headers that may be added for all ICAP adaptation requests.

The following protocol-specific header is added to the ICAP request headers:

  • X-Transformed-From

    The value is SMTP.

The following headers are set on the HTTP PUT request:

  • Content-Type

    The value is message/rfc822 for the SMTP DATA payload.

  • X-SMTP-From

    The value is the reverse-path from the SMTP MAIL command, containing the sender’s mailbox address.

  • X-SMTP-To

    The value is the forward-path from the SMTP RCPT command, containing the recipient mailbox address. This header appears multiple times when there is more than one recipient.

The body of the HTTP PUT request contains the SMTP message data.

Not Implemented

  • BDAT message.

  • BURL message.

These unsupported extensions are disabled by default in the auditor’s smtp interception configuration.